Pressure-operated emergency switch



TCH

Filed Aug. 2l, 1953 i omww ululllanhlr jm. mm

United States Patent Oiilice 2,728,073

Patented Dec. 20, 1955 cylindrical opening or bore 16 in the supportingblock 13. The upper end of the aneroid 14 is supported resiliently by acoil spring 17, one end of which abuts a 2,728,073

PRESSURE-OPERATED EMERGENCY SWITCH Robert J. Kelly, Berkley, Mich.

A l' t' A 1t21 1953 S l .375 838 bracket 21. Thf angular bracket 21 SlXed, 3S by a. pp Ica mn ugub erm No machine screw 22, to a block 23,which block is secured 4 Claims. (Cl. 340282) l0 to the panel 11 as bymachine screws 24. n The adjustment screw 20 and its locking nut 20a are(Granted undvr Title 35 U' S' Code (1952) sec' 266) provided to allowpreliminary setting of the aneroid at The invention described herein maybe manufactured l5 position with respect to the adjustable lower contact26,

and used by or for the Government of the United States hereinbelowdescribed. of America for governmental purposes without the pay- As theaneroid is carried aloft in an aircraft, reduced ment of any royaltiesthereon or therefor. pressure will, of course, cause the aneroid toexpand, so This invention relates to pressure-operated electrical thatits upper end will move outwardly, in the direction switches, and isdirected particularly to a barometric opposite that indicated by thearrow. pressure-operated device for deenergizing aircraft elec- Theupper contact comprises an oval metallic sleeve trical circuits at apredetermined critical altitude. For clamped, as by screws 27, about theouter end of an L- example, selected circuits can be opened or groundedshaped bracket 28 The other end of bracket 28 is fixed just before aforced landing in order to minimize the to the top of the aneroid 14 soas to be movable therepossibility of fire. 25 with. The contact 25 isinsulated electrically from This application is a continuation-in-partof my cobracket 23 by an intermediate bushing or sleeve 29, prefpendingapplication Serial No. 256,809, filed November erably of rubber. Thelower contact 26, similarly, is 16, 1951, for improvements in PressureOperated Emerclamped to and insulated from a supporting arm 30. gencySwitch, now abandoned. The lower end of the supporting arm 30 isjournalled It is common knowledge that one of the great hazards 30swingably on a pin 31 secured between a spaced pair of ofaircraft crashlandings is the possibility of ignition of upstanding brackets 32, 33fixed to the panel 11 as by spilled gasoline by damaged electricalwiring. The batscrews 34. tery power supply can either becomeshort-circuited per- A coil tension spring 35 is connected at one end inmanently and heat to the kindling temperature of the an apertured ear 36extending from the outer end of gasoline vapor, or it can shorttemporarily, creating a 35 the supporting arm 30, and at its other endto the panel spark hot enough to cause ignition. Also, the high-ten- 11as by a screw 37, thereby serving to urge the supsion engine-ignitionvoltage wiring energized by the magporting arm 30, together with itscontact 26, in the neto can become damaged, and if the engine is stillclockwise or upward direction. functioning at the time of the crash, asoften happens, Calibrated means for adjusting the position of thehigh-tension sparks to metallic parts of the aircraft could 40supporting arm 30, and hence the position of the lower start a fire.contact 26 with respect to upper contact 25, is provided. Accordingly,it is one object of this invention to pro- A half-threaded adjustmentscrew 38 extends perpenvide a switching device for automaticallydeenergizing dicularly through the panel 11. The inner end of adtheelectiical circuits of a disabled or abandoned airjustment screw 30 isin abuttinfy alignment with the end craft at a predetermined time beforethe landing of the edge of the supporting arm 30, said arm beingconaircraft. strained thereagainst by action of the tension spring 35Another object is to provide a device of the character A pair of plates39, 40 welded or otherwise fixed described at can be preset to becomeoperative at a against opposite sides of the supporting arm 30, havepredetermined elevation above sea level. outwardly flared-end portions41, 42, respectively, ex- A further object is to provide apressure-operated tending beyond the end edge of said supporting arm toswitching device incorporating a signal panel for indiprovide a track orguide for the inner end of adjustment eating visually the selectedelevation at which the device screw 38. will operate. The underside ofknurled head 43 of the adjustment Other objects and many of theattendant advantages screw 38 has fixed thereagainst, as by a flatretaining nut of this invention will be readily appreciated as the same44, a Centrally apeffufed CCCTCaUY Conductive disk 45- becomes betterunderstood by reference to the following A vertical bracket 46 mountedagainst the underside of detailed desciiption when considered inconnection with Panel 11 has a VeUCal edge 1H 0103 Proximity t0 the theaccompanying drawings wherein: edge of the disk 45, said vertical edgehaving marked Fig. l is a side elevational view of the pressure switchthereon a scale of elevation indicia whereby the operator together withits associated Wiring and signal panel, showcan preset the adjustmentscrew 38 to the position correing a preferred embodiment of theinvention; and sponding with any selected elevation at which the deviceig. 2 is a partial, vertical cross-section of Fig. l taken Will beCOmeOPfaVe- Thus, if the adlusmenf SCTSW along the line 202 thereof. wereset for operation at 0 elevation, or sea level, the Similar numeralsrefer to similar parts throughout the action of the aneroid 14, uponbeing brought down to several views. sea level, would move the upperContact 25 into electri- The pressure-operated switch unit 10 comprisesa base cal contact with the lower contact 26. if the adjustment plate orpanel 11, of electrical-insulation material, SCreW 38 Were Set fOrOperaioll at 2000 feet, Contact against which is secured, as by a pairof screws 12 (only 26 would 0f COUTS@ be at a higher POSOU S0 aS t0 beone shown), a wedge-shaped aneroid supporting block contacted by contact25 at a barometric pressure corre- 13. The lower end of an aneroid 14 isfixed in inclined 70 sponding to an elevation of 2000 feet. relationshipwith respect to the panel 11 by having its The upper and lower contacts25 and 26 control a cylindrical leg 15 seated and held frictionallywithin a circuit comprising the onoff switch 48, the aircraft lowvoltage supply battery 49, a solenoid relay 50 for deenergization of thelow voltage supply wiring, an a solenoid relay 51 for shorting theaircraft magneto to ground.

rlhe relay Sil is provided with a pair of switch contacts 50a and 50h,interconnected normally by the shorting arm 50c but adapted to becomeopen-circuited and remain open-circuited when the energization coil 50dof said relay is energized and withdraws its plunger 50e.

The relay l. is provided with a pair of switch contacts 51a and Sib,open-circuited normally but adapted to become short-ciruited when theenergization coil 51d of said relay is energized and withdraws itsplunger Sie and associated shorting arm Slo.

The relay-energization coils Sd and 51d are connected in parallel bywires 52 and 53, said parallel circuit being connected in series withthe aircraft ground and the upper terminal by wires d.- and 55respectively.

rThe lower contact 26 is connected by a wire 5o to one terminal of theon-off switch d8, the other terminal Lof which is connected by wires 57and 53 to the positive terminal of the aircraft battery 4E-9. The relaycontacts a and Slb are interconnected by a wire 59, and grounded byconnection with the grounded wire The relay switch contact tlb isconnected by a wire 6l) to the negative terminal of the aircraft batterydl).

The above-described circuit operates as follows: Upon descending from ahigher elevation to the elevation at which the pressure-operated switchis set to operate, the

contacts 2.5 and 26 will touch each other, as hereinl above detailed,completing energizing circuit to the relays 50 and Si.. Said circuit canbe traced from ground, through wires 54 and 59, through normallyclose-circuited contacts Sila and Stlb of relay 5t), through wire 6l) tothe negative terminal of the aircraft power supply battery 49, thence,from the positive terminal thereof through wires 58, 57, now closedon-off switch 4S, wire Se, through now contacting lower and uppercontacts 26 and 25, thence, from contact Z5, through wires and 53 to oneterminal each of the energization coils 5M and 51d of the relays Se and5l respectively, thence, from the remaining terminals of said relays,through wires 52 and 54 back to aircraft ground.

The relay Slt is of a type that is faster acting than the relay 50, sothat upon energization it will operate to short the magneto primary ofthe aircraft to ground before the relay 50 operates to open-circuit theaircraft battery ground circuit.

The magneto grounding circuit, effective upon actuation of the relay 5l,can be traced from ground, through wires 54 and 59, through the nowshorted relay contacts Sla and 511; to a wire leading to the aircraftignition magneto.

Operation of the relay 5l) will, of course, open-circuit the connectionfrom the negative terminal of the aircraft battery 49 to ground, wherebyaccidental shorting of damaged wiring to ground to cause sparking orheating of the wiring will be prevented.

The switch 43 and the head 43 of the adjustment knob 33 are mountedpreferably so as to be controlled readily from the pilots position infront of the instrument panel.

In order that the pilot can determine readily the elevation at which theemergency device is set to operate, a signal-light panel 6l, locatedpreferably on the instrument panel, `is provided.

The signal light panel el comprises a plurality of lamps 62, each ofwhich has one terminal grounded by being connected to the common groundwire 63. rl`l1e other terminals of the lamps are connected individuallyby the wires 64, 65, 6o, 67, 63 and 59 to a contact device comprising aplurality of piled contactors 7l?, 7l, 72, 75, 74, interspaced andinsulated from each other by insulation pieces 76, and fixed against theunderside of the panel 1l in abutting relation to the metallic disk 45by a pair of machine screws 77 and a plate 78. Thus,

as the adjustment screw 3S is turned outwardly, for increasing theelevation of operation of the emergency switch, the metallic disk l5will make contact successively with the contactors 7o, 7l, 72, 73, 74,75. The insulation pieces 76 are each thicker than disk d5 to preventsimultaneous contact of said disk with more than one of said contactors7tl to 7S. These connections, through a circuit hereinbelow detailed,furnish energizing voltages to the individual lamps with which they areconnected, which lamps are marked in elevations from t) to 10,00() feetin 200G foot increments, to corerspond with the elevation readings onthe scale of bracket 46.

Connection to the metallic disk 4S is made through a spring brush '79having one end iiXed to the panel ll and the other end pressingresiliently against the innermost end of the metallic adjusting screw38. Thus, no matter to which position the adjusting screw 3S is set,electrical connection between the spring brush 79 and the metallic disk45 will be complete. A wire 80 connects the spring brush 79 to wire 5o,to complete the electrical circuit for the panel 6l.

The energizing circuit for the panel lamps can be traced from thepositive terminal of the battery 4%, through wires 5 and 57, closedswitch d8, wires 56 and Si? through the spring brush 79, adjusting screw38, and the metallic disk 45 to the particular contacter with which isin Contact (t) elevation in the drawing), thence to the lamp associatedtherewith to energize it through its connection to ground.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. lt is therefore to beunderstood that within the scope of the appended claims the inventioncan be practiced otherwise than as specifically described.

l claim:

1. ln an electrical control of an electrical system ernY bodying asource of electrical energy and a generator of electricity in proximityto an inflammable, a control circuit embodying a normally-open relaycomprising a solenoid operable to short circuit and deenergize thegenerator, a normally-closed relay switch in the line of the electricalsource and comprising a solenoid operable to open the line, a set ofcontacts operable to close the electrical-control circuit, and aninstrument operable responsive to atmospheric pressure to actuate thecontacts relative to each other into contacting engagement to close thecontrol circuit at a predetermined atmospheric pressure, the severalrelay solenoids being connected in parallel in the control circuit andcomprising respective electrical characteristics to operate thegenerator-control relay rst to deenergize the generator and thereafterto operate the relay controlling the electrical energy source to openits line.

2. The electrical control as delined in claim l for control of theelectrical system of an aircraft of which the magneto of the engineignition constitutes the generator and the battery constitutes thesource of electrical energy, the generator-control relay operating toshort circuit the magneto to ground, and the relay controlling theelectrical-energy source operating t0 open the battery line.

3. A pressure operated switch comprising a normally spaced pair ofelectrical contacts, means responsive to barometric pressure and adaptedto move one of said contacts to a plurality of positions, said pair ofcontacts being in contact with each other at one of said positions,means for adjusting the position of the other of said contacts, anelectrical circuit including said contacts, a voltage source in saidcircuit, a normally-closed electrical switch in series with said voltagesource in said circuit, first solenoid rneans to open saidnormally-closed electrical switch upon energization thereof, saidsolenoid being energized through said normally-closed electrical switch,a normally-open electrical switch, second solenoid means to close saidnormally-open electrical switch upon energization thereof, theenergizing windings of aid first and second solenoid means beingconnected in parallel, said rst soleoid means being faster-acting thansaid second solenoid means, whereby said normallyselectively lighttheposition of said other contact, height at which said pressure-operatedoperate.

4. A pressure-operated switch comprising a normally spaced pair ofelectrical contacts, means responsive to barometric pressure and adaptedto move one of said contacts to a plurality of positions, said pair ofcontacts being in Contact with each other at one of said positions,means for adjusting the spacing between said pair of contacts, anelectrical circuit including said contacts, a voltage source in saidcircuit, a cal switch in series with said voltage source in saidcircuit, rst solenoid means to open said normally-closed electricalswitch upon energization thereof, said solenoid being energized throughsaid normally-closed electrical switch, a normally-open electricalswitch, second solenoid means to close said normally-open electricalswitch upon enerUization thereof, the energizing windings of said rstand second solenoid means being connected in parallel, said rst soleoidmeans being faster-acting than said second solenoid means,

whereby said normally-closed References Cited inthe le of this patentUNITED STATES PATENTS

